I am glad I asked. Here is a simple way to reset your maps.
1. Do not be in a game as later steps could cause your client to crash.
2. Locate your saves folder in the ATLauncher.
3. Inside this folder you should see two mapwriter folders and you want the “mapwriter_mp_worlds” folder.
4. Inside this folder are all the servers you have connected to and you just need to delete which ever server you are wanting to reset the map.
An example of where my map files would be: